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Cerebral haemorrhagic contusion

Cerebral haemorrhagic contusions are a type of intracerebral haemorrhage and are common in the setting of significant head injury.

Epidemiology

Contusions, by definition, result from head trauma, and are thus seen more frequently in young males. Typical causes include motor vehicle accidents or situations in which the head strikes the pavement. 

Pathology

Most contusions represent the brain coming to a sudden stop against the inner surface of the skull (contrecoup) accentuated by the natural contours of the skull (see below). 

Radiographic features

Cerebral contusions can occur anywhere, but have a predilection for certain locations, as a result of the direction of head strike and the intrinsic shape of the skull cavity. 

Furthermore the appearance of contusions will vary according to when they are imaged. Typically they mature over a number of weeks, initially appearing as merely haemorrhagic foci, followed by the development of surrounding oedema, before gradually fading away leaving behind more or less obvious areas of gliosis

CT

In most hospitals CT is usually the first and often only investigation used to assess cerebral contusions. Sensitivity to detect intracerebral haemorrhage on CT scans is virtually 100%.

Hounsfield units (HU) of blood are dependent of protein concentration (i.e. haemoglobin) and haematocrit.

With a haematocrit of 45% the density of whole blood is ~56 HU while grey matter is 37-41 HU and white matter is 30-34 HU. So blood should be hyperdense in comparison to grey or white matter.

Of note, in anaemic patients (i.e. haemoglobin < 8-10 g/dL) blood may appear isodense in an acute bleeding.

Typically contusions appear as foci of hyperdensity involving the grey matter and subcortical white matter. 

MRI

Although not often used merely for the assessment of superficial contusions, MRI is far more sensitive to small contusions, especially when T2* sequences, i.e. SWI, are used.

Signal behaviour is strongly dependent on sequence and time since the bleeding started.

Practical pearls and pitfalls

A pitfall is missing a small contusion near the skull base, which can be overseen on CT scans due to partial volume artefact

See also

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